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Questions tagged [thermodynamics]

Covers the study of (mostly homogeneous) macroscopic systems from a heat/energy/entropy point of view. Consider also using tag: [statistical-mechanics].

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How to connect the force applied to a tuning fork and the intensity of sound produced mathematically [on hold]

I'm in year 11 and I have a science depth study where I get to conduct and record an experiment of my choosing to do with sound or light waves. I've chosen to conduct an experiment where I am trying ...
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0answers
18 views

Second Law of Thermodynamics and Thermal Pollution

Unlike coal power plants which produce CO2 and intensify the greenhouse effect, every engine produces thermal pollution because of the constraints on engine efficiency. No engine can convert 100% of ...
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1answer
50 views

Convert emotion into energy? [on hold]

if it were possible to quantify emotion, would it be possible, theoretically, to then convert it into usable energy?
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5answers
11k views

Have researchers managed to “reverse time”? If so, what does that mean for physics?

According to press releases, researchers have reversed time in a quantum computer and violated the second law of thermodynamics. What does that mean for physics? Will it allow time travel? Further ...
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2answers
56 views

Question about the definition of the pressure in statistical physics

I learned, that the definition of the pressure in the grand canonical ensemble is $p=-\langle \frac{\partial H}{\partial V}\rangle=\frac{1}{\beta}(\frac{\partial}{\partial V} \ln\Xi$. First thing ...
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1answer
26 views

How can I calculate the pressure needed to compress a piece of tubing with a liquid inside?

I want to study the optical properties of a molecule under pressure. The method that I am planning to use to apply the pressure on my sample is the following: A silicone rubber tube is connected to ...
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1answer
40 views

How to find equation of state of an ideal gas from heat capacity?

I'm having a problem where I have to derive the equation of state of an ideal gas from the formula for molar heat capacity $C=C_V+ \beta V$. Is this even ideal gas? Can someone help me, or at least ...
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1answer
54 views

Why is detailed balance required for thermodynamic consistency?

why does the Wegscheider condition or detailed balance have to be true for chemical reactions and what does it mean to violate it in terms of thermodynamics? here is an attempt to derive a simple ...
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3answers
1k views

Quasistatic vs Reversible processes

Would it be fair to state the difference between quasistatic and reversible processes as follows?: A process is quasistatic if at every point in the process the system is in equilibrium with itself. ...
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2answers
48 views

Can Entropy Change be negative in this situation?

The temperature of two moles of an ideal diatomic gas is decreased from 𝟔𝟎𝟎 𝐊 to 𝟑𝟎𝟎 𝐊 at constant pressure. Is entropy change negative?
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2answers
59 views

Temperature of vacuum chamber on Earth

Does the temperature of a vacuum chamber drop if left for 24 hours or more, since some in space in quite cold somewhere and quite hot how does vacuum become cold near to absolute zero.
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3answers
76 views

Can we concentrate the “cold of the sky” with a parabolic dish to cool things down during the day?

It's well known that we can focus sunlight with a parabolic dish to collect heat. But if we look at the thermal images of the sky we can see that the clear blue sky is quite cool. So by turning the ...
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1answer
168 views

Microscopic explanation of colligative properties from the entropy related viewpoint

In the chapter 28.6 of book "Concepts in thermal physics "(2nd edition) written by Stephen J. Blundell, there is a sentence says "Adding a small quantity of solute to a solvent increases the entropy ...
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4answers
31 views

Does positive total entropy generation means that the entropy generation of the system and the entropy generation of the surroundings are positive too

When I was working on problems related to entropy generation, there was this problem that asks if the process claimed in the problem is possible or not. The solution manual calculated the total ...
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0answers
79 views

How everyone can benefit from learning physics? [on hold]

What would be benefits of learning physics in a relatively rigorous way (meaning to take a quick look even at the topics that are more advanced, like quantum field theory) for people who don't aspire ...
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3answers
35 views

Partial molar volume and constant composition

Why is it necessary that the composition of a mixture (with 2 components A and B) remains constant to arrive at this equation $$ \begin{aligned} V &=\int_{0}^{n_{A}} V_{\mathrm{A}} \mathrm{d} n_{\...
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2answers
118 views

Relative humidity, definition and its dependence on state variables

Relative humidity ($RH$) is defined by the following equation: $$ RH = \frac{p_{vap}}{p_{sat}} $$ Where $p_{vap}$ is the vapour pressure and $p_{sat}$ is the saturation vapour pressure. VAPOUR ...
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2answers
170 views

Can the increase of entropy be decreased?

I know in an isolated system entropy always tends to increase, but what about the speed of that increase (e.g. the acceleration of entropy-the derivative of its speed)? Is there any law or relation ...
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2answers
54 views

Could a refrigeration unit be used to provide useful heating?

I was thinking about refrigerators and air conditioners. They remove the heat from somewhere and put it into somewhere else. But why are we use this usually for cooling, and not so much for heating (I ...
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1answer
58 views

How does a gas lamp mantle work? Is it just black body radiation?

Old gas lighting often involved a thing called a "mantle" which was a cloth mesh coated with thorium dioxide. The gas flame heated the mantle and the mantle gave off the indoor lighting that people ...
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8answers
7k views

How large would the steam explosion at Chernobyl have been?

So the second episode of the HBO series began to cover the risk of a steam explosion that led to them sending three divers into the water below the reactor to drain the tanks. This occurred after the ...
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1answer
53 views

Negative Temperature Without Statistical Mechanics

In plenty of the qualitative thermodynamics that predates the statistical description, temperature is assumed to always be positive; many key inequalities related to the second law often involve ...
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0answers
13 views

ferromagnetic above the Curie temperature paramagnetic?

Why is a ferromagnet above the Curie temperature a paramagnet? Considering me, it's because a paramagnet has a higher entrope and since $\frac{1}{T} = \frac{\partial S}{\partial E}$. If T increases ...
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2answers
122 views

Difference between Phonons and heat?

1, if these two were the different then how we differentiate with one another?. 2, if these two were the same, then what is really vibrating?, atom in the lattice or electron in the atom or the bond ...
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0answers
37 views

Grand-canonical ensemble for $dln \mathcal{Z}$ [on hold]

I really don't understand how this is done, I understand the first line, but then it looks like de canonical ensemble relations are used, but this is about the grand-canonical ensemble. Essentially I ...
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1answer
22 views

Tea steeping as a function of infuser

Suppose I have two identical cups, but one has a spherical steel tea infuser and the other has a muslin, both with the same amount of tea. I add boiling water to both. Assume both the infuser and the ...
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1answer
109 views

How do you measure the chemical potential?

It is clear how to measure thermodynamics quantities such as temperature, pressure, energy, particle number and volume. But I have no idea how to measure chemical potential. Could someone please ...
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1answer
100 views

Why is pizza soggy after microwaving?

Compared to when heated over fire, pizza is soggy when heated in a microwave oven. I want to know why this is. So far I’ve just learnt that microwaves in ovens are of a specific frequency of ...
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3answers
79 views

Infinite entropy in ideal gas

Does it make sense that entropy goes to infinity as temperature goes to infinity? For an ideal monoatomic 1D gas I have an expression for entropy \begin{equation} S=Nk_{B}Ln(\frac{Ve^{\frac{5}{2}}\...
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1answer
48 views

joule-thomson coefficient

I'm a little bit in trouble with this table on wikipedia (https://en.wikipedia.org/wiki/Joule%E2%80%93Thomson_effect ) Since it says that when the temperature is below the inversion temperature($1/\...
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1answer
176 views

Temperature change of water and the copper can

The question is: "0.38kg of a liquid at 12 degrees C is heated in a copper can weighing 0.9kg by an electrical heater of power 20W for 3 minutes. It reaches a temperature of 17C. Assuming no heat loss ...
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3answers
66 views

Entropy generation of constant volume heat addition process

For an ideal gas constant volume heat addition process, change of entropy equation is: $$\Delta S= c_v \ln\frac{T_2}{T_1}+ R \ln\frac{v_2}{v_1}= \int \frac{dq}{T}+S_{gen}$$ The term $R \ln\frac{...
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1answer
275 views

Why don't we observe spontaneous symmetry restoration in nature?

Why do we always observe spontaneous symmetry breaking in nature and not restoration? Does there exist some argument with the 2nd law of thermodynamics and the entropy of the universe increasing? If ...
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No Schottky anomaly in the case of the heat capacity $C_{V}(T)$ of a harmonic oscillator?

Why is there no Schottky anomaly in the heat capacity $C_{V}(T)$ of a harmonic oscillator? There are Schottky anomalies present in 2-level/N-level systems with equal spacing between levels. ...
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0answers
19 views

Schottky anomaly in the heat capacity $C_{V}(T)$ of a 2-level system

Why does the Schottky anomaly in the heat capacity ($C_{V}(T)$ against $T$) associated with a 2-level system with energy spacing $E$ appear at $k_{B}T\approx\frac{E}{2}$ (a precise calculation gives $...
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0answers
26 views

At thermal equilibrium, do the energies of the 2 systems equalize?

Suppose we have 2 systems with energies $E_1$ and $E_2$ respectively that are in contact with each other until thermalization occurs. The temperatures of the 2 systems equalize but do the energies $...
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4answers
115 views

First law of thermodynamics differential form doubt

For the first law of thermodynamics, we have that $Q-W=\Delta U$ Since there is a variation of the values of the thermodynamic variables, because of Q and W, there is a variation of internal energy....
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1answer
15 views

Can a non-quasi-static process have an equation of the path which it has followed?

Recently I saw a question where there was a specific p-v relation for a process, but it was stated that it's not a quasi-static process. Hence, we can not calculate the work done by integration of pdv ...
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0answers
28 views

Should it work?(waterless cooling system) [on hold]

The presented Idea is based on Heat exchange principle. As per sketch there will be a conveyor belt system and some copper stripes will be connected with this belt. Each copper strip will have a ...
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1answer
128 views

How to formulate surface temperature of a material exposed to sunlight and wind?

I am currently searching for a model or an approach (reference, course, demonstration) to formulate and estimate surface temperature of a known material (for example, concrete, metal), exposed to ...
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0answers
47 views

What does this paper talk about? and Does Ricci flow have some application in general relativity? [on hold]

https://arxiv.org/abs/gr-qc/0602054 who has read and studied this paper, and if we can apply ricci flow to GR? if so, it is known that ricci usually is limited in positive remiann manifold, and ...
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3answers
360 views

Meaning of the term “phase” in chemistry and thermodynamics

I have some doubts about the definition of the term “phase” in chemistry and thermodynamics (is the meaning the same?). The "textbook" definition is: "A phase is a form of matter that is uniform ...
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1answer
230 views

What is the relationship between flow work and velocity of gas?

As we know that for open systems, we have energy conservation equation as $$h+\frac{v^2}{2}+zg=const.$$ $$h=u+pV$$ $$u+pV+\frac{v^2}{2}+zg=const.$$ Here $pV$ is flow energy. We know that all these ...
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1answer
38 views

boundary conditions in QM and statistical physics

I don't understand something about boundary conditions in problem that I discuss it below. in QM we solve the particle in Potential well and we obtain that we should have $k=\frac{n*pi}L$ that $n\in{...
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1answer
27 views

Absence of dissipative forces in a reversible process

I can't understand why dissipative forces must be absent during a reversible transformation. Aren't they a way of exchanging heat with ambient? Since the system is allowed to exchange heat with the ...
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2answers
30 views

A heat flow generalized problem featuring light bulb and oven

If an incandescent light bulb under constant power is taken from room temperature 25 deg C to an oven at 75 deg C, does the filament temperature increase by 50 C? Assume radiated power is negligible ...
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2answers
159 views
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How can work be generated from quantum correlations?

There are several articles (like this or this one) concerning extracting work from (quantum and/or classical) correlations. Nevertheless, these articles appear to be quite dense and without showcasing ...
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1answer
56 views

How does sound melt concrete?

The sound power level (SPL) of the Saturn V rocket engines were 220 db. There are numerous websites that state this is loud enough to melt concrete. An example from the website makeitlouder.com 220 (...
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0answers
52 views

If we assume constant Temperature and Pressure, why isn't the Change in Gibbs Free Energy always 0?

The Gibbs Free Energy is defined as: $$G = U + PV - TS$$ If we assume that the temperature $T$ and the Pressure $P$ are constant, then any change in the Gibbs Free Energy would be: $$\Delta G = \...
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1answer
179 views

Reversible engines

As far as my understanding goes, the only reversible heat engine is the Carnot engine, described by the Carnot cycle. On the other hand, in all of the resources I've found the change in entropy for ...